This invention relates to a method and apparatus for reducing, in fumes containing condensable elements, the content of non-condensable gaseous elements which are soluble in these condensable elements.
More particularly, the purpose of the present invention is to provide a method and apparatus for reducing the HCl content in fumes containing water vapor, which are produced by the incineration of waste products such as household garbage.
Indeed, the destruction through incineration of waste products containing chlorine, mainly in the form of plastic chlorinated substances (especially polyvinyl chloride - PVC), leads to the presence of gaseous HCl in the fumes in varying amounts according to the source of the waste products. For example, for household garbage, the average HCl content is about 1 g/Nm.sup.3 under standard evaluation conditions (7% CO.sub.2 or 11% O.sub.2) for which the maximum release amounts have been determined.
U.S. Pat. No. 2,592,812 describes a method and apparatus for reducing the amounts of acidic pollutants in fumes from which dust has been removed and which have been subjected to a cooling phase before being released into the atmosphere. In this procedure, the fumes are cooled at a temperature lower than their dew-point temperature, thereby producing condensation of the water vapor.
Thus, the fumes which are discharged from the heat-exchanger device are saturated with water vapor, and the harmful pollutants still present are in solution in the water droplets.
It is, therefore, necessary to install, downstream from the heat-exchanger device, a device for the removal of vesicles which captures the droplets being released from this exchanger.
The droplets generated by a device of this kind are very small, since they are the product of condensation in situ, in the fumes, of the water vapor around condensation cores. Thus, the vesicle-removal device, which may be a Venturi tube, uses excessive amounts of energy and easily becomes clogged with soot. Furthermore, this vesicle-removal device generates a loss of load on the order of 300 daPa.
To do without this vesicle-removal device, different installation arrangements have been suggested, all of which are based on the reheating of the fumes before releasing them in a non-saturated state.
In any event, the installation of the vesicle-removal device or the reheating system is complicated, burdensome, and difficult to maintain.